" Angina is the pain you get when there’s not enough oxygen getting to your heart muscle for the work it’s doing. That’s why it gets worse with exercise: because you’re demanding more work from the heart muscle. You might get a similar pain in your thighs after bounding up ten flights of stairs, depending on how fit you are. Treatments that help angina usually work by dilating the blood vessels to the heart, and a group of chemicals called nitrates are used for this purpose very frequently. They relax the smooth muscle in the body, which dilates the arteries so more blood can get through (they also relax other bits of smooth muscle in the body, including your anal sphincter, which is why a variant is sold as ‘liquid gold’ in sex shops). In the 1950s there was an idea that you could get blood vessels in the heart to grow back, and thicker, if you tied off an artery on the front of the chest wall that wasn’t very important, but which branched off the main heart arteries. The idea was that this would send messages back to the main branch of the artery, telling it that more artery growth was needed, so the body would be tricked. Unfortunately this idea turned out to be nonsense, but only after a fashion. In 1959 a placebo-controlled trial of the operation was performed: in some operations they did the whole thing properly, but in the ‘placebo’ operations they went through the motions but didn’t tie off any arteries. It was found that the placebo operation was just as good as the real one—people seemed to get a bit better in both cases, and there was little difference between the groups—but the most strange thing about the whole affair was that nobody made a fuss at the time: the real operation wasn’t any better than a sham operation, sure, but how could we explain the fact that people had been sensing an improvement from the operation for a very long time? Nobody thought of the power of placebo. The operation was simply binned. That’s "
― Ben Goldacre , Bad Science